Relief valve for flue system



Nov. 12, 1968 E. E HAJEK RELIEF VALVE FOR FLUE SYSTEM 3 Sheets-Sheet 1 Filed May 1, 1963 INVENTOR. ERNEST E. HAJEK BY 5 Z ATTORNEY Nov. 12, 1968 E. E. HAJEK RELIEF VALVE FOR FLUE SYSTEM I5 Sheets-Sheet 2 Filed May 1, 1963 K a m m M V N T 3 I 5 Z 2 E M N w E Y! B J & a

ATTORNEY Nov. 12, 1968 E. E. HAJEK RELIEF VALVE FOR FLUE SYSTEM 5 Sheets-Sheet 5 Filed May 1, 1963 INVENTOR. E RN EST E.

JEK BY f ATTORNEY United States Patent 3,410,288 RELIEF VALVE FOR FLUE SYSTEM Ernest E. Hajek, Richmond, Calif., assignor to Kaiser Industries Corporation, Oakland, Calif., a corporation of Nevada Filed May 1, 1963, Ser. No. 277,198 7 Claims. (Cl. 13771) This invention relates to an emergency relief valve and particularly to a device to relieve rapidly the pressure and vent the gases in a gas-collecting and conducting system of a basic oxygen steel making process.

Although the device of this invention may have use in other processes, it isparticularly adapted for use in the basic oxygen steel making process. In this process iron is converted to steel by maintaining molten iron, scrap and slag-forming materials in an open-mouthed converter and blowing a stream of oxygen downwardly onto the surface of the metal in the converter. During the resultant conversion process many reactions take place which result in the evolution of a large volume of hot, dust-laden gas.

A-flue system or assembly is employed to carry oh the hot gases evolved from the process. The flue system ineludes gas-conducting ducts, means for precipitating or otherwise removing the dust carried in the gas, and an induced draft fan to draw the gas through the flue system. The flue assembly may also include coolers, means for recovering waste heat, and means for recovering combustible gas to mention a few of the additional devices that may be employed.

The fan is usually placed to discharge into a stack. The fan is placed near the stack in order to be near the discharge end of the system and, therefore, in the coolest environment and because of this location, it places most of the flue system under a slight negative gauge pressure.

During the operation of the flue system emergency conditions may arise which are dangerous to personnel and which could cause damage to the expensive flue system. One serious emergency condition that may occur is an explosion of the combustible gas within the flue. Another emergency condition is overheating due to burning of the gases in the flue and another is the production of a greater volume of hot gas than the blower can remove. Still another emergency condition is the failure of the blower. Through the use of this invention these hazards are abated or greatly diminished.

The emergency relief valve of this invention includes a large cross-section vent, preferably having substantially the cross-section of the ducts in the gas-conducting system, said vent being placed adjacent the main stream in the gas-conducting system and generally upstream of the dustcollection devices and on the suction side of the fan. The vent is relatively short and it is positioned to conduct gas in the flue system to an innocuous or unhazardous discharge point, for example, on the roof of and outside of the building which houses the processing equipment. The vent is sealed with at least one and preferably two or more hinged or pivotally connected flaps which form a seal by the force of gravity causing them to lean either against each other or against portions of the vent or both. Gravity holding the flaps in position as well as the negative pressure within the flue system causes the flaps to seal the opening of the emergency relief valve. In the context of this specification and the appended claims, the term seal is 3,410,288 Patented Nov. 12, 1968 not to be construed as an absolute gas-tight seal but a seal that offers high resistance to the passage of gas and one which is consistent with the closures and connections found elsewhere in the same gas-conducting and collecting system.

The flaps are operated to be opened by a hydraulic or pneumatic motor or other equivalent means which can operate by remote manual control or responsive to a sensing device that is positioned within the duct system to sense a dangerous condition in the system. The sensing means is connected to a controller in the usual way and the controller converts and amplifies signals from the sensing means to'actuate or energize the motor. The motor, accordingly, operates responsive to the signals from the sensing means. Sensing means such as thermocouples, pressure responsive elements, relays, etc., to mention a few, which may be used alone or in combination are those contemplated for use in this invention.

When the pressure within the duct system becomes too high because of an explosion, the inadequacy of the blower, partial or complete plugging of the flue system, or burning within it, a dangerous condition exists and the operation of the device of this invention causes the relief valve to open thereby venting the entire flue system to the atmosphere outside of the building which houses the process. Accordingly, hot burning gases are conducted from the flue system and cannot injure personnel or damage equipment by rupture or thermal damage.

In one modification of this invention one or more flaps of the relief valve is provided with a rupture plate made of thin gauge thermally resistant metal or other material. In the event of an explosion or pressure surge, the pressure through the flue system frequently will be so rapid that the operation of the motor in the relief valve will be too slow to relieve the system before damage can be done. In this embodiment, the rupture plate will be blown or torn by the force of the pressure surge to provide an immediate opening to relieve the major pressure while the flaps are being opened by the normal operation of the motor. Thus, damaging, rapidly accumulating pressure may be relieved immediately while ordinary high pressure in the system is relieved by the ordinary operation of the sensing device, controller and motor that operates the flaps. Since the rupture plate must be relatively large in diameter, preferably at least three or four feet, and of such thin gauge that it will rupture immediately and to a major extent when it is subjected to relatively small positive pressure in the flue system, the rupture plate of this invention will preferably be supported on the underside by some perforated element, such as a screen or an expanded metal plate. The slight negative pressure in the vent system will hold the rupture plate against the screen and the support given by the screen will prevent rupture of the plate by providing many points of intermediate support. By this means, pressure due to the normal operation of the blower will work in effect against a series of rupture plates, each having an effective diameter the size of the screen openings, perhaps one-quarter of an inch. But when there is positive pressure in the vent, the force against the rupture plate which tends to push it out and away from the screen operates against the entire area of the plate which, as heretofore mentioned, may be three or four feet in diameter. In this way, a rupture plate capable of withstanding large negative pressure, but one that will rupture under very small positive pressure, is obtained.

In another modification of this invention the hinged flaps forming a closure of the relief valve may be connected to open by the positive pressure of an explosion independently of or in addition to the force exerted by the motor. In the event of an explosion creating a large pressure surge, the pressure surge itself will cause the relief valve flaps to open before the motor operates thereby again providing for immediate relief of the initial pressure surge. This embodiment of the invention is provided by the use of an elongated, relatively movable connection between the motor and the flaps, such as slots or rails, whereby force exerted by the motor immediately causes the flaps to open, but force exerted from within the flue system, as by a pressure surge, may force the flaps to open even though the motor is not operating since relative motion between the motor and its connection to the flaps is provided for by the rails, slots or equivalent means.

This invention can best be understood with reference to the accompanying drawings which are presented as illustrative of one device embodying this invention but are not intended as limiting the scope of the invention to the device illustrated.

FIGURE 1 is a partial schematic representation of a basic oxygen conversion process employing the device of this invention;

FIGURE 2 is an elevation view of an emergency relief valve embodying this invention and showing in broken lines one open position that the device may occupy;

FIGURE 3 is a sectional view of the relief valve of FIGURE 2;

FIGURE 4 is a perspective view of the device of FIG URE 2; and

FIGURE 5 is a partial sectional view along the line 5-5 in FIGURE 2.

A typical converter which is a refractory-lined, open-topped vessel containing a charge of molten iron, scrap iron, and flux-forming material is employed in conjunction with a flue system generally designated 11. An oxygen lance 12 is shown extending through vent system 11 and into converter 10 in such position that it may discharge oxygen onto the surface of the charge in the converter. The connections for oxygen and cooling water are conventional and not shown herein. The lower portion of the flue system is normally water cooled while the upper portions are refractory lined. The flue system includes a vertical portion 13, an angular portion 15, an electrostatic precipitator 16, an inlet 17 connecting to the suction side of a fan 18 which discharges into a stack 20. As stated heretofore, FIGURE 1 is schematic and shows only basic and fundamental elements of the flue system which may include heat recovery means, gas recovery means, and other devices. The entire process is housed within a structure that is not shown except for the roof 21 through which the stack 20 extends.

Also extending through the roof 21 is the emergency relief valve of this invention which is designated generally as 22. It is shown here with a short vent portion 23 that extends directly from the main vertical flue assembly 13, flaps 25 and 26 and a motor 27. The device of this invention is also provided with a sensing means 28 which connects to a controller 30 through a line 31 that is appropriately chosen to transmit variations in electric energy, pressure, temperature, etc., whereby the extent of the condition sensed by sensing means 28 is transmitted to controller 30. Ordinarily a simple off-on control, such as a pressure switch or temperature-operated microswitch, which switches operate valves, is all that is required. Sensing means 28 is shown and positioned schematically in that it may be positioned any place in association with the flue system, such as in the precipitator, in the fan intake, in the electric circuit of the fan, etc.

In normal operation hot gas evolving from the converter 10 enters the flue system 11 and passes through vertical portion 13, and then downwardly through angular portion 15 and through precipitator 16, Where the dust in the converter gas is removed, after which the converter gas is passed through the inlet 17, the fan 18 and discharged through stack 20. The entire flue system up to fan 18 is on the suction side of the fan and, accordingly, is under a slight negative gauge pressure, that is, a. pressure less than atmospheric pressure. As a result, air is sucked into the flue system rather than converter gases being discharged through any openings or leaks.

When the gas flue system is operating at an abnormal condition so that the temperature in the flue system rises to its maximum allowable temperature, a temperature sensing means at 28 operating through controller 30 and line 32 will actuate the motor 27 to open flaps 25 and 26 whereby the excessively hot gas is immediately vented through vent 23 and into the atmosphere outside of the structure in which the process is being effected. Thus, the interior of vertical portion 13 is open directly to the atmosphere so that gas may be removed simply by passing from the vent 23 as well as by way of angular portion 15 and fan 18. When the operation returns to normal, and the temperature at sensing means 28 reduces, the controller will cause the motor operating means in line 32 to cut off and flaps 25 and 26 will return to their normal sealed position.

When the volume of gas at any temperature exceeds the amount that fan 18 can handle in normal operation, the pressure in the flue system, particularly in vertical portion 13, will increase and a pressure sensing means located as at 28 will cause controller 30 to operate the motor 27 as described previously to open flaps 25 and 26 and to relieve the pressure. Of course, the flaps 25 and 26 should not be opened until the pressure in the flue system 11 exceeds atmospheric pressure in that opening these flaps when the flue system is at subatmospheric pressure will tend to load the fan more thereby aggravating the unsatisfactory condition. Pressure due to other causes, such as plugging of the flue system in the precipitator, will also cause the emergency relief valve to open, and it is further within the scope of this invention to cause the emergency relief valve to open when the fan ceases to operate for any reason and to be opened by an operator from a remote control point. It is apparent that other sensing means and normal instrumentation may be employed in lieu of or in addition to those mentioned to open flaps 25 and 26 when other emergency conditions exist and, if desired, to close them when the emergency conditions cease to exist.

The details of one embodiment of the emergency relief valve of this invention are best shown in FIGURES 25. The relief valve generally designated as 22 in FIGURE 1 is shown in FIGURE 2 separate from the flue system it is employed to protect. A vent- 23 which connects to the flue system consists of a box-like connection that is substantially as large in cross-section as the flue system. Tapered walls 35 are connected to the vent element 23 and the flaps 25 and 26 form a seal with walls 35 and with each other when they lean against each other. The motor 27 is shown here as a pneumatic or hydraulic cylinder having a line 36 for the introduction of operating fluid and a line 37 for removal of operating fluid. The cylinder 27 is conventional and suitable restoring means are provided for returnnig it to the retracted or flap-closing position when the operating fluid pressure is relieved. The motor 27 has shafts 38 and 40 extending from it, and these shafts are normally in contact with the end of slotted elements 41 and 42. As shown in solid line representation in FIGURE 2, when cylinder 27 is in flap-closing position, flaps 25 and 26 are closed, and the connections of shafts 38 and 40 with elements 41 and 42 are such that operation of the cylinder 27 to extend the shafts 38 and 40 will immediately cause flaps 25 and 26 to open.

The slotted elements 41 and 42, as shown here, are constructed with slots that are arcs of the circumference of the circle whose centers are at hinges 43 and 45. The slots designated here as 46 and 47 are large enough to accommodate loosely the connection between shafts 38 and 40 and slotted elements 41 and 42. By this means a sudden surge of pressure within the flue system 11 will cause flaps 25 and 26 to pivot around hinges 43 and 45 and open independently of the operation of motor 27. The flaps in such open position are illustrated in broken line representation in FIGURE 2. I

Another means for providing immediate pressure relief is shown best in FIGURES 3 and 5 which are sectional views illustrating .a rupture plate or disc inserted in flap 25. One possible design is that the flap 25 consists of an outer metal shell and an inner refractory lining 51. An opening 52 which may be of any shape but is preferably circular extends through both the metal shell 5 0 and the refractory lining 51. Within the opening there is positioned .a perforated element such as a screen or expanded metal element 53 which is constructed of heat resistant material and which is in supporting contact with a sheet of thin, heat resistant material, such as copper, shown at 55. The thickness of this sheet is selected with relationship to its diameter so that any positive superatmospheric pressure or positive gauge pressure from within the emergency relief valve 22 which is sufficient to harm the flue system will cause the sheet or rupture disc 55 to rupture thereby opening the interior of the flue system 11 to the atmosphere and relieving the pressure. The screen is connected as by welding to the inner port1on of the metal element 50, the rupture disc 55 is placed on the screen 53 and in contact with it, and an appropriately shaped ring 56 held with bolts 57 holds the periphery of the rupture disc 55 against the screen 53 to restrain it in its normal operating position.

As stated heretofore, the embodiment shown in the drawings is to be considered a typical embodiment and a presently preferred form of the invention, but it is by no means limiting on the scope of the invention. The relief valve of this invention may employ one flap which may be vertical, horizontal, or at any angle to the horizontal. The conditions sensed to actuate the controller may be any of those mentioned or any others that appropriately indicate when an emergency condition requiring relief of the pressure in the system exists. Also, although particularly appropriate for the oxygen conversion process, the emergency relief valve of this invention may be used in any flue system where relief of the system will provide protection when an emergency condition exists. Having thus described the invention.

What is claimed is:

1. An emergency relief valve for a flue system for carrying gas which comprises means defining a vent in the flue system, a pivoted flap positioned to be held by gravity in sealing relationship with said vent, a motor connected to move said flap out of sealing relationship with said vent, and means responsive to a condition within said flue system to actuate said motor, wherein said flap is provided with an opening and said opening is sealed with a rupture disc comprising a perforated member on the exterior side of which a sheet of heat resistant material is placed, said sheet having a thickness such that it is readily ruptured by a small positive gauge pressure in said flue system.

2. An emergency relief valve for use in an oxygen steelmaking process having a flue system for carrying gas from said conversion process comprising a fan in said flue system, a vent on the suction side of said fan, a pivoted flap positioned to be held by gravity into sealing relationship with said vent, said flap being formed to define an opening, a perforated member fixed in said opening and a rupture disc placed on the exterior side of said perforated member, a motor connected to move said flap out of sealing position with said vent, and means responsive to an emergency condition within said flue assembly to actuate said motor.

3. The relief valve of claim 2 wherein said vent is sealed by a plurality of flaps.

4. An emergency relief valve for a flue system for carrying gas which comprises means defining a vent in the flue system, a pivoted flap positioned to be held by gravity in sealing relationship with said vent, motor means having a drive shaft and adapted upon actuation to move said shaft and thereby to move said flap out of sealing relationship with said vent, an element connected to said flap and having an arcuate slot concentric with the pivot axis of the flap, a connection between the element and the drive shaft, said connection being slidable in said slot so that an opening motion of said flap effected independently of said motor means results in a sliding motion between said element and said shaft, and means responsive to a condition within said flue system to actuate said motor means.

5. In a flue system including a duct adapted to carry exhaust gases under pressure and having an upwardly directed vent, an emergency relief valve for opening and closing said vent comprising wall means connected to said duct and projecting upward therefrom adjacent to said vent and defining an outlet located in a plane that is at an acute angle with the horizontal, flap means pivotally connected to said wall means for movement between a closed position covering said outlet wherein said flap means is disposed in said plane and an open position spaced from said outlet wherein said flap means is disposed in a plane that is also at an acute angle with the horizontal but greater than the acute angle of the plane of said outlet, said flap means being capable of freely pivoting from its closed position to its open position under emergency conditions when pressure in said duct reaches a predetermined level, said flap means being capable of freely gravitationally pivoting from its open position to its closed position when pressure in said duct drops below said level, actuatable powered means having a movable drive shaft and linkage means slidably interconnecting said drive shaft and said flap means for enabling said powered means to move said flap means from closed position to open position upon actuation of said powered means and for enabling said flap means to pivot to said open position under said emergency conditions, and subsequently to return to closed position, without powered movement of or prevention by said drive shaft, said linkage means limiting movement of said flap means in the open position thereof.

6. In the flue system of claim 5, said linkage means including a slotted element connected to said flap means, said slotted element providing an arcuate slot that lies on a circle concentric with the pivoting arc of said flap means, and connecting means between said slotted element and said drive shaft, said connecting means being slidably received in said slot.

7. In an upwardly opening vent, and a pair of flaps pivoted on the vent on spaced parallel pivot axes for movement through a limited arc between positions closing the vent in which the flaps are upwardly converging and positions opening the vent in which the flaps are also upwardly converging but are angularly displaced from said closing positions, a mechanism for moving said flaps between said opening and closing positions comprising a double-acting motor means extending between said flaps and having a pair of shafts individually adjacent to said flaps, slotted elements individually connected to the flaps, each element having an arcuate slot concentric with the pivot axis of its associated flap, and connections individually slidable in said slots and connecting the associated shaft and slotted element, said motor means being operable to actuate said shafts thereby causing said shafts to bear against their respective flaps to move the same to opening positions, sliding of said conneetions through said slots permitting movement of each flap between opening and closing positions independently of said motor means.

7 References Cited UNITED STATES PATENTS 898,071 9/1908 Shannon 26626 1,664,493 4/1928 Smith 137488 1,983,521 12/1934 Cooke 236-49 2,287,433 6/1942 Klafstad 137-468 XR 10 553,956 2/1896 Coultas.

8 Flindall 137513 X Schullstrom 137492.5 Galusha 137-68 X McKune 251-82 X Cooper 137115 X Philip 137-68 X Sjogren 25182 Konernund 137527.5

WILLIAM F. ODEA, Primary Examiner.

R. GERARD, Assistant Examiner. 

1. AN EMERGENCY RELIEF VALVE FOR A FLUE SYSTEM FOR CARRYING GAS WHICH COMPRISES MEANS DEFINING A VENT IN THE FLUE SYSTEM, A PIVOTED FLAP POSITIONED TO BE HELD BY GRAVITY IN SEALING RELATIONSHIP WITH SAID VENT, A MOTOR CONNECTED TO MOVE SAID FLAP OUT OF SEALING RELATIONSHIP WITH SAID VENT, AND MEANS RESPONSIVE TO A CONDITION WITHIN SAID FLUE SYSTEM TO ACTUATE SAID MOTOR, WHEREIN SAID FLAP IS PROVIDED WITH AN OPENING AND SAID OPENING IS SEALED WITH A RUPTURE DISC COMPRISING A PERFORATED MEMBER ON THE EXTERIOR SIDE OF WHICH A SHEET OF HEAT RESISTANT MATERIAL IS PLACED, SAID SHEET HAVING A THICKNESS SUCH THAT IT IS READILY RUPTURED BY A SMALL POSITIVE GAUGE PRESSURE IN SAID FLUE SYSTEM. 